NAME

vmstat − report virtual memory statistics

SYNOPSIS

vmstat [ −fsi ] [ drives ] [ interval [ count ] ]

DESCRIPTION

vmstat delves into the system and normally reports certain statistics kept about process, virtual memory, disk, trap and cpu activity. 

If the following arguments are given, the other statistics will be reported. 

−f the number of forks and vforks since system startup and the number of pages of virtual memory involved in each kind of fork. 

−s the contents of the sum structure, giving the total number of several kinds of paging related events which have occurred since boot. 

−i the number of interrupts taken by each device since system startup. 

If none of these options are given, vmstat will report in the first line a summary of the virtual memory activity since the system has been booted.  If interval is specified, then successive lines are summaries over the last interval seconds.  ‘vmstat 5’ will print what the system is doing every five seconds; this is a good choice of printing interval since this is how often some of the statistics are sampled in the system; others vary every second, running the output for a while will make it apparent which are recomputed every second.  If a count is given, the statistics are repeated count times.  The format fields are:

procs: information about numbers of processes in various states. 

r in run queue

b blocked for resources (i/o, paging, etc.) 

w runnable or short sleeper (< 20 secs) but swapped

memory: information about the usage of virtual and real memory.  Virtual pages are considered active if they belong to processes which are running or have run in the last 20 seconds.  A ‘page’ here is 1024 bytes. 

avm active virtual pages

fre size of the free list

page: information about page faults and paging activity.  These are averaged each five seconds, and given in units per second. 

re page reclaims (simulating reference bits)

at pages attached (found in free list)

pi pages paged in

po pages paged out

fr pages freed per second

de anticipated short term memory shortfall

sr pages scanned by clock algorithm, per-second

disk: Disk operations per second (this field is system dependent).  Typically paging will be split across several of the available drives.  The number under each of these is the unit number. 

faults: trap/interrupt rate averages per second over last 5 seconds. 

in (non clock) device interrupts per second

sy system calls per second cs cpu context switch rate (switches/sec)

cpu: breakdown of percentage usage of CPU time

us user time for normal and low priority processes

sy system time

id cpu idle

If more than 4 disk drives are configured in the system, vmstat displays only the first 4 drives.  To force vmstat to display specific drives, their names may be supplied on the command line. 

FILES

/dev/kmem
/vmunix

SEE ALSO

systat(1), iostat(1)

The sections starting with “6.5 Monitoring System Performance” in Installing and Operating 4.3BSD(SMM:1).

NEWS-OSRelease 4.2.1R